<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        canvas {
            border: 1px solid;
        }
    </style>
</head>

<body>
    <canvas width="500" height="500" id="mycanvas"></canvas>

    <script>

        let obj = {
            bg1: "https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fimg.jj20.com%2Fup%2Fallimg%2Ftp02%2F1Z9191923035R0-0-lp.jpg&refer=http%3A%2F%2Fimg.jj20.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1661397561&t=a620034e48d31890e7e652561c79083b", bg2: "https://img2.baidu.com/it/u=1713796643,4188877777&fm=253&fmt=auto&app=138&f=JPEG?w=889&h=500", bg3: "https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fimg.jj20.com%2Fup%2Fallimg%2Ftp05%2F1Z9291TIBZ6-0-lp.jpg&refer=http%3A%2F%2Fimg.jj20.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1661397561&t=d113fcaf5515f719281a37f6e928b213"
        };

        function loadImg(obj, cb) {
            return new Promise((resolve) => {
                let length = 0
                for (let key in obj) {
                    length++
                }

                console.log('对象的长度', length)
                // 记录图片加载好的数量
                let count = 0
                // 循环加载对象里的图片
                let resObj = {}
                fot (let k in obj) {
                    let imgEle = new Image()
                    imgEle.src = obj[k]
                    imgEle.onload = function() {
                        count++
                        resObj[k] = this
                        if (count >= length) {
                            // 所有图片加载完毕
                            cb && cb(resObj)
                            resolve(resObj)
                        }
                    }
                }
            })
        }
        // loadImg()



    </script>
</body>

</html>